A version of this
article originally appeared in Guns Review International, February 1996.
Last update 25 September 2010.

The history of British military rifle cartridges
in the twentieth century was not a happy one. At the beginning of the
century, the .303 inch, one of the first of the small-bore military
cartridges, had been in service for a dozen years and was already being
criticised as obsolescent and inadequate. Attempts to introduce a
satisfactory replacement were initially stymied by the onset of World
War 1, then in the interwar period by a lack of resources, and finally
- twice - by demands for NATO standardisation. As a result, British
troops throughout the century and up to the present day have been
equipped with small arms using cartridges which have been less than
ideal. Ironically, one cartridge which did see limited British service
early in the century could have made a much better basis for military
small arms than anything which has seen service since; the Japanese
6.5x50SR (popularly known as the 6.5mm Arisaka), designated in British
service "the .256 inch".

British Rifle Cartridges Development to
World War 2

The .303" cartridges in service early in the
century were of various Marks, some with a hollow point to improve
stopping power (withdrawn soon afterwards as they contravened the
1899 Hague Convention which banned expanding bullets), but all had
heavy round-nosed bullets fired at a low muzzle velocity. The
performance of the .303" Lee Enfields in the Boer War of 1899-1902 was
regarded as unacceptably inferior to the relatively high velocity 7mm
Mauser weapons of the Boers, as the open country of the South African
plains favoured a flat-shooting, long-range rifle.

As a result, work began in 1910 on a replacement,
suitable for long-range rifle fire, which emerged in 1912 as the .276
inch Enfield cartridge, chambered in the new "Rifle, Magazine, Enfield
.276 inch Pattern 1913" bolt-action rifle - a modification of the
well-known Mauser rifle. The cartridge was impressive and had
performance to match; not far short of present-day 7mm Remington Magnum
ballistics. Not surprisingly, troop trials in 1913 revealed problems
with excessive recoil, muzzle flash and barrel wear and overheating.
Attempts were made to find a cooler-burning propellant, but further
trials were halted by the events of 1914. As a result, the .303" was
retained in service, albeit in the much improved Mark VII loading with
a lighter, pointed bullet and a higher muzzle velocity to provide a
better long-range performance and, like other pointed bullets, a
tendency to yaw on impact magnifying the wounding effect . This
remained the standard rifle ammunition until the .303" was replaced by
the 7.62x51 NATO in the mid-1950s.

At this point of the story, the .256 inch British
makes its appearance. Early in World War I a considerable shortage of
Lee Enfield rifles occurred. As a result, the UK purchased no less than
130,000 Japanese Arisaka service rifles of assorted types, all in
6.5x50SR calibre, a designation Anglicised into .256 inch
(representing the bore diameter). These were mainly used for training
and home defence but were also issued to some naval units. From 1916
they were all shipped to Russia, and it appears there were none left by
the end of the war. The rifle was a conventional, if rather long, bolt
action weapon, but the cartridge had an unrecognised potential which we
will return to later.

It was fortunate that the .276" Enfield was not
adopted, as even the .303" proved unnecessarily powerful for the
predominantly short-range trench warfare of 1914-1918. By this time, a
further problem with the .303" was becoming obvious; the rimmed case
design was not well suited to most fully-automatic weapons. Much
experimentation with semi-rimless and rimless cartridges took place
between 1917 and the late 1920s to no avail. Despite considerable
interest being shown in the (subsequently cancelled) American Pedersen
rifle and its relatively low-powered medium-velocity .276" ammunition
(which would have been well-suited to automatic rifles), the
combination of severe economic problems and vast quantities of standard
.303" weapons and ammunition in store after the First World War
militated against the adoption of any new calibre. The 1930s rearmament
programme therefore saw such weapons as the American Browning aircraft
machine gun and the Czech ZB30 (better known in its British incarnation
as the Bren Gun) expensively redesigned to fire the rimmed cartridge.

World War 2 Experience and Aftermath

Experience in the Second World War reinforced the
point that Britainís standard rifle ammunition, in common with that of
other nations, was unnecessarily powerful for most engagements. It was
capable of shooting accurately out to 1,000 yards (and ranging out to
over 4,000 in the streamlined Mark VIII version for the Vickers Machine
Gun), yet almost all fire-fights took place at less than 300 yards.
This might not have mattered, except that the advantages of
fully-automatic fire in rifles had also become obvious, and this was
not feasible with full-power military rifle cartridges because their
heavy recoil made automatic rifle fire uncontrollable.

The 1939-45 conflict saw both the acceptance of the
sub-machine gun as an important military weapon and the introduction of its
eventual replacement; the assault rifle. The need for a weapon with the
automatic fire of a submachine gun but the range to cope with most infantry
engagements was first realised in Germany. This led to the introduction of the
MP44 Sturmgewehr (assault rifle), firing a new 7.92x33Kurz
(short) cartridge with a performance intermediate between the standard
7.92x57 rifle/MG round and the 9mm sub-machine gun cartridge. The
Soviet Union soon followed suit with the 7.62x39 M1943 round, due for
international fame in the Kalashnikov AK and AKM assault rifles but
also used in other weapons including light machine guns.

After the Second World War, both the USA and the
UK gave much thought to the introduction of new small arms cartridges.
The British, together with Belgium and with the support of Canada,
developed a 7x43 round (also known as the .280" and, in slightly
modified form, the .280/30") and the associated EM-2 "bullpup" assault
rifle, similar in configuration to the current 5.56mm L85A2 Army
weapon. The calibre, bullet weight and muzzle velocity were carefully
calculated to combine the low recoil necessary for automatic fire with
a sufficiently long range to replace the .303", by all accounts
successfully. The compact bullpup layout was chosen so that the EM-2
could replace the 9mm Sten SMG as well as the Lee Enfield rifle.

The US Army also produced a smaller round to
replace their .30'06 and as a competitor to the British 7mm for the
standard NATO small arms cartridge, but appeared to suffer from
considerable confusion over the purpose of the new round. They decided
both to retain the .30" calibre and to provide sufficient power to
replace the .30'06 in machine guns, thereby ensuring that the new
cartridge was too powerful for an assault rifle. Selective fire was
provided in some rifles, but the recoil made automatic fire
uncontrollable. The 7mm supporters protested but American military and
economic power prevailed, saddling NATO with the 7.62x51NATO cartridge which was no real advance over the 50-year old 30'06.

Having committed NATO to a cartridge too powerful to
permit the development of assault rifles to match the Kalashnikov, the US Army
decided as a result of experience in Vietnam that it had made a mistake and went
to the other extreme in adopting the .223" (5.56x45) round for the M16 assault
rifle. This acquired a controversial reputation in Vietnam, with tales of the
devastating effect of the high-velocity bullets conflicting with other accounts
criticising the lack of range and penetration. As a result, the 7.62mm NATO
remained in US service and has indeed experienced a revival in recent years
since the 5.56mm has proved unable to cope with the long-range engagements
common in Afghanistan.

Other NATO countries began to consider replacing
the 7.62mm (at least in the standard infantry rifle) in the 1970s, and
a competition for a new cartridge was held. The British proposed a
4.85mm round but ensured that it was based on the 5.56mm cartridge so
that the weapons designed for it could easily be converted in the event
of the US cartridge winning the NATO competition; which (to no-oneís
surprise) it did. Since then, much further research into future
military rifles involving such exotic concepts as caseless ammunition
and flechette (steel dart) rounds has taken place but it seems that the
5.56mm NATO may be with us for the foreseeable future, supported by the
7.62mm where more range or hitting power are required.

6.5mm Rounds: Past and Present

So where does the .256" British fit into this?
The answer lies in a series of experiments conducted by the British and
Americans to discover the ideal military small arms calibre. In the
late 1960s, the Royal Small Arms Factory at Enfield began a detailed
theoretical analysis of the striking energy needed to disable soldiers
with various levels of protection, and the ballistics required to
deliver that energy at battle ranges for a number of different
calibres. The conclusion was that the optimum calibre would lie between
6mm and 6.5mm, and an experimental 6.25x43 cartridge (based on the
abortive 7mm round) was developed which was claimed to have significant
advantages over both the 5.56mm and 7.62mm calibres. Performance proved
to be virtually equal to the 7.62mm at up to 600 metres, with recoil
and ammunition weight much closer to those of the 5.56mm.

At the same time, the US Army realised the need
for a light machine gun with a longer effective range (out to 800
metres) than the 5.56mm cartridge could provide but appreciably less
weight than the 7.62mm M60 MG. Their research led to the development of
the 6mm SAW (Squad Automatic Weapon) cartridge. A relatively heavy
bullet combined with a moderate velocity were selected for the optimum
long-range performance. In the event, weapons firing improved 5.56mm
ammunition were selected instead, largely to avoid the supply problems
created by the use of three small-arms calibres. More recently, the US
firm of Alexander Arms has introduced the 6.5mm Grendel, a cartridge
which matches the 7.62mm NATO in its long-range performance with much
less weight and recoil.

Returning to the .256" British, it is now clear
that the 6.5mm calibre is a much better compromise for a
general-purpose military rifle and machine-gun cartridge than either
the 5.56mm or the 7.62mm. So why did the Japanese (and most other
nations with 6.5mm weapons) develop larger and more powerful calibres
in the 1930s? This is worth exploring in some detail.

The main reason is that cartridges were optimised for machine guns,
which in those days were far more commonly used for long-range (including
indirect) fire than they are today, with ranges in excess of 2,000 metres
sometimes used. So powerful 7.5-8mm ammunition was required, and several rounds
were introduced in the 1920s and 1930s specifically to meet this need: the
Japanese 7.7x58SR and 7.7x58, the Swedish 8x63, Norwegian 8x57, Italian 8x59
Breda and Austrian 8x56R Solothurn. Sometimes these rounds were also available
in rifles (mainly in the interests of simplifying supply), but it is worth
pointing out that the Japanese Army's 7.7mm ammunition was available only in
machine guns for a decade before it started to be used in rifles. Replacing the
6.5mm in rifles was clearly not a priority.

Another reason probably lies in the relatively
ineffective loadings used in most 6.5mm cartridges at the time, usually
featuring heavy, round-nosed bullets and low velocities. Such bullets
not only have poor ballistics but also do not yaw on impact, instead
punching a neat hole which causes only minor injuries unless it hits a
vital organ. From 1905 the standard Japanese loading (the Type
38) was much better, with a pointed bullet giving good ballistics
(interestingly, closely matching those of the 7mm EM-2) and, according
to WW2 US Army medical reports, very good terminal effectiveness with
rapid yaw on impact causing severe wounds. However, British production
of the cartridge concentrated on the earlier round-nosed Type 30 since
its ballistics matched the sights of the older Arisaka rifles acquired
in large numbers by Russia, to which most of the ammunition was
shipped. Confusingly, the Type 38 saw British service first so was
known as the Mark I, with the older Type 30 being designated Mark II.

The final reason for the emphasis on larger and more
powerful cartridges was that the requirement for automatic fire from rifles did
not exist until World War 2. As a result, neither did the need to reach a
compromise between ballistic performance and the reduced recoil needed for
controllable automatic fire. So the potential of the 6.5mm calibre in combining
excellent long-range ballistics with moderate recoil and ammunition weight was
not recognised.

The .256 inch cartridge is not entirely ideal for
modern military purposes as it is semi-rimmed rather than rimless, and
with modern powders the cartridge case could be smaller and lighter.
Nonetheless, its potential was recognised very early in Russia, which
used the Japanese cartridge in the Federov Avtomat, a selective-fire
rifle first produced in 1916. If it had remained in British service as
a supplement to the .303", preferably in a modified, rimless, form and
with a lighter bullet at a higher velocity (8g at 800 m/s - 123
grains at 2,620 fps - should have been possible) the .256" cartridge
could have provided an excellent basis for a family of light,
fully-automatic weapons in time for World War 2, and could still
provide a better all-round compromise than the ammunition in service
today. Its problem was that it entered British service about 30 years
ahead of its time.

CARTRIDGES AND BALLISTICS (AT THE MUZZLE)

Cartridge

Metric Size mm

Bullet Weight

in Grains

Velocity fps

Energy ft/lbs

.303" Mk II

7.7x56R

215

2,000

1,920

.303" Mk VII

7.7x56R

174

2,440

2,312

.276" Enfield

7x60

165

2,800

2,888

.256" British Mk 1

6.5x50SR

139

2,500

1,930

.280" British

7x43

139

2,530

1,986

6.25mm British

6.25x43

100

2,680

1,603

4.85mm British

4.85x49

56

2,950

1,088

7.92mm Kurz

7.92x33

125

2,250

1,413

7.62mm M1943

7.62x39

122

2,330

1,478

5.45mm Soviet

5.45x39

54

2,950

1,049

7.62mm NATO

7.62x51

150

2,750

2,532

5.56mm USA

5.56x45

55

3,200

1,257

5.56mm NATO

5.56x45

61

3,050

1,267

6mm SAW

6x45

105

2,520

1,488

Further information on the history of assault
rifles and their ammunition is HERE.